Reversible Peristaltic Pump and Other Structures for Reflux in Eye Surgery

ABSTRACT

Devices, systems, and methods for treatment of an eye alter aspiration flow from the eye in response to an occlusion of the aspiration conduit pathway. Where aspiration is drawn from the eye using a volumetric pump, the pump can be reversed so as to induce fluid reflux from the aspiration conduit pathway into the eye to help clear the occlusion. The pump may vary the reverse flow in response to sensed aspiration pressure or the like, and the reverse flow may be halted before the pressure within the aspiration conduit pathway adjacent the eye significantly exceeds the irrigation fluid pressure and/or the pressure within the eye. Reflux may alternatively be generated by modulating a vent valve disposed between an irrigation conduit pathway and the aspiration conduit pathway.

RELATED APPLICATION

The present application claims priority under 35 U.S.C §119(e) toprovisional application No. 60/865,163, filed on Nov. 9, 2006 under thesame title. Full Paris Convention priority is hereby expressly reserved.

BACKGROUND OF THE INVENTION

The present invention is generally related to methods, devices, andsystems for controlling surgical fluid flows, often during treatments ofan eye. In exemplary embodiments, the invention allows clearing of anocclusion in an aspiration conduit pathway during (for example) cataractsurgery or the like, optionally by reversing a peristaltic aspirationpump, modulating a vent valve between the aspiration conduit pathway andan irrigation fluid source, or the like.

With age, clouding of the lens or cataracts are fairly common. Cataractsmay form in the hard central nucleus of the lens, in the softerperipheral cortical portion of the lens, or at the back of the lens nearthe capsular bag. Cataracts can be treated by the replacement of thecloudy lens with an artificial lens. Phacoemulsification systems oftenuse ultrasound energy to fragment the lens and aspirate the lensmaterial from within the capsular bag. This may allow the capsular bagto be used for positioning of the artificial lens and for maintainingthe separation between the anterior portion of the eye and the vitreoushumor in the posterior chamber of the eye.

During cataract surgery and other therapies of the eye, accurate controlover the volume of fluid within the eye is highly beneficial. Forexample, while ultrasound energy breaks up the lens and allows it to bedrawn into a treatment probe with an aspiration flow, a correspondingirrigation flow may be introduced into the eye so that the total volumeof fluid in the eye does not change excessively. If the total volume offluid in the eye is allowed to get too low at any time during theprocedure, the eye may collapse and cause significant tissue damage.Similarly, excessive pressure within the eye may strain and injuretissues of the eye.

While a variety of specific fluid transport mechanisms have been used inphacoemulsification and other treatment systems for the eyes, mostaspiration flow systems can generally be classified in one of twocategories: 1) volumetric-based aspiration flow systems using positivedisplacement pumps; and 2) vacuum-based aspiration systems using avacuum source. Among volumetric aspiration systems, peristaltic pumps(which use rotating rollers that press against a flexible tubing toinduce flow) are commonly employed. Cassette systems can be used tocouple peristaltic pump drive rotors or vacuum systems of the surgicalconsoles to an eye treatment handpiece, with the flow network conduit ofthe cassette being disposable to avoid cross-contamination betweendifferent patients.

While existing cataract surgery devices, systems, and methods haveproven highly effective and have helped numerous patients, still furtherimprovements and refinements remain desirable. For example, bothvolumetric and vacuum-based aspiration remain (to varying degrees)subject to temporary blockage or occlusion of the aspiration flow. Asultrasound energy breaks up the lens structure within the eye, small andsoft tissue particles are readily drawn into an aspiration port of thetreatment probe. Unfortunately, larger and/or harder tissue particlesmay at least temporarily cover the aspiration port of the probe,impeding flow of material and fluids from the eye into the probe. Theultrasound energy transmitted by the probe, in combination with theaspiration pump, often (though not always) eventually break up theoccluding particle and successfully withdraw the occlusive material intothe probe and from the eye. Unfortunately, significant fluid pressuretransients can occur during this process. While existing eye treatmentsystems have structures that can successfully clear many or allocclusions, known occlusion clearing approaches may actually increasepressure transients, and/or may rely on complex and costly systemcomponents. More generally, current occlusion clearing methodologies mayhave either a relatively slow response time or insufficient pressurecontrol.

In light of the above, it would be advantageous to provide improveddevices, systems, and methods for eye surgery. It would be particularlyadvantageous if these improvements allowed occlusions of an aspirationconduit pathway to be cleared without subjecting the eye to excessivepressure surges, serious underpressurization, or other undesiredpressure excursions or transients. It would be particularly advantageousif these improvements could be provided without excessively increasingthe complexity, cost, or difficulty in using these sophisticated eyetreatment systems.

BRIEF SUMMARY OF THE INVENTION

The present invention generally provides improved devices, systems, andmethods for treatment of an eye. Exemplary embodiments allow alterationof an aspiration flow in response to a request by the user and/or anocclusion of the aspiration conduit pathway. In some embodiments, mostoften (though not necessarily) where aspiration is drawn from the eyeusing a volumetric pump, the pump is reversed so as to provide ventingof the aspiration conduit pathway or induce fluid reflux from theaspiration conduit pathway into the eye to help clear the occlusion. Thereversing of the pump may be halted before the static pressure withinthe aspiration conduit pathway reaches a predetermined value. Forexample, sufficient reflux may be induced to clear occlusions, with thereflux being produced at least in part from the momentum of fluid withinthe aspiration conduit pathway toward the eye. In other embodiments,reflux may be generated by continuing to drive a volumetric pump in thereverse direction, by modulating a vent valve disposed between anirrigation conduit pathway and the aspiration conduit pathway, or thelike.

In a first aspect, the invention provides an eye treatment methodcomprising directing an irrigation flow into the eye through anirrigation conduit pathway. Material is aspirated from within the eye bydrawing an aspiration flow through an aspiration conduit pathway with apump. In response to a user request and/or an occlusion of theaspiration flow, the pump is reversed and fluid is pumped back into theaspiration conduit pathway, for example, to reflux flow into the eye tohelp clear the occlusion.

Optionally, the pump may comprise a volumetric pump such as aperistaltic pump or the like. The occlusion may induce a compliantreduction in volume of the aspiration conduit pathway between the eyeand the pump. Reversing the pump may at least partially compensate forthe reduction in volume, allowing the aspiration conduit pathway toreturn back toward its pre-occlusion size. The pump speed may bemodified in response to a variation in pressure along the aspirationconduit pathway between the pump and the eye, and/or to anotheraspiration parameter or characteristic. Reversing of the pump may behalted when a pressure of the aspiration flow adjacent the eye is lessthan or substantially equal to an irrigation flow pressure at the eye sothat the reflux into the eye is largely generated by momentum of theaspiration conduit pathway toward the eye. The reflux may be primarilygenerated by the momentum, and in some embodiments may be entirelygenerated by the momentum, rather than relying on any reflux-inducingstatic pressure differential between the pump-generated pressure and thepressure within the eye.

In many embodiments, a substantially constant reverse pumping flow rateor pump speed may be maintained while the absolute pressure of anaspiration conduit is below a threshold. In other embodiments, thereverse pumping flow rate or speed may vary as a particular function ofa system parameter while the absolute pressure of an aspiration conduitis below a threshold. For example, when an aspiration line pressure isbetween zero and a first threshold, the flow rate or pump speed may beconstant or determined using a first linear relationship between flowrate (or pump speed) and line pressure. A second linear relationship maybe applied when the line pressure is between the first threshold and asecond threshold (e.g., atmospheric pressure). A third linearrelationship may be applied when the line pressure is between the secondthreshold and a third threshold (e.g., between atmospheric pressure andan irrigation bottle pressure). Further thresholds may be employed tofurther segment the value of the flow rate or pump speed. Also, one ormore of the linear relationships may be replaced by non-linearrelationships between the pumping flow rate (or pump speed) and a systemparameter such as aspiration line pressure. Other system parameters mayinclude an irrigation pressure, a temperature, and the like.

The irrigation and aspiration flows may be initiated by actuation of afoot pedal input device. For example, irrigation flow may be initiatedby movement of the foot pedal from a nominal undeflected position to afirst position. Aspiration flow may be added to the irrigation flow bymoving the foot pedal from the first position to a second position.Energizing of a probe through which the aspiration flow is withdrawnfrom the eye may be added by moving the pedal from the second positionto a third position. A surgeon or other system user may release thepedal, allowing it to return to the nominal position, when the occlusionof the probe is recognized, and the pump may be reversed while the footpedal is in the nominal position. In other embodiments, the system mayinitiate reversal of the pump and reflux, or the surgeon may input acommand to initiate reflux without returning the foot pedal to thenominal position.

The reversing of the pump may be controlled in response to a change orrate of change of aspiration pressure, a pressure of the irrigationflow, a height of the eye of the patient, and/or the like. The height ofthe eye of the patient may be estimated from the height of an accessorytray of the system (the tray normally being at or near the patient's eyelevel). The pressure of the irrigation flow may be related to a heightof an irrigation fluid container, and the height of the irrigationcontainer may be driven and/or sensed by a controller.

In some embodiments, a vacuum source may be coupled to the aspirationfluid conduit by an aspiration selector valve, for example, so thataspiration flow may be induced by either the vacuum source or thevolumetric pump. The aspiration selector valve will typically bepartially or completely closed (so that the vacuum source does notaffect pressure within the aspiration conduit pathway) during reversingof the pump.

In another aspect, the invention provides an eye treatment methodcomprising directing an irrigation flow into the eye through anirrigation conduit pathway. Material is aspirated from within the eye bydrawing an aspiration flow through an aspiration conduit pathway. Inresponse to an occlusion of the aspiration flow (the occlusion typicallyinducing a compliant reduction in volume of the aspiration conduitpathway), fluid may be introduced into the aspiration conduit pathway.The introduction of fluid into the aspiration conduit pathway may becontrolled in response to a pressure along the aspiration conduitpathway so that a maximum reflux pressure within the aspiration conduitpathway adjacent the eye is less than, or substantially equal to, anirrigation flow pressure adjacent the eye or some other predeterminedpressure. As a result, reflux into the eye is generated at least in partby momentum in the aspiration conduit pathway toward the eye.

The material may be aspirated from the eye using a peristaltic (or othervolumetric) pump, and the fluid may be introduced into the aspirationconduit pathway by reversing the peristaltic pump. In other embodiments,the material may be aspirated from the eye using a vacuum source such asvacuum pump (optionally being a Venturi pump, a rotary vane pump, or thelike). The fluid may be introduced into the aspiration conduit pathwayby opening a valve between the irrigation conduit pathway and theaspiration conduit pathway. Alternatively, another higher pressuresource my be used in place of the irrigation pathway, for example thehigh pressure side of the aspiration pump. The introduction of the fluidmay be controlled by modulating the valve in response to the pressurealong the aspiration conduit pathway, so that the valve provides avarying flow resistance.

In another aspect, the invention provides an eye treatment systemcomprising an eye treatment probe and an eye treatment console having aprocessor and an aspiration pump drive. A cassette couples the probe tothe processor and/or console. The cassette has a pressure sensordisposed along an irrigation conduit pathway for determining anirrigation flow pressure into the eye via the probe. The cassette andprobe have an aspiration conduit pathway coupled to the pump foraspirating material from within the eye. The processor of the console isconfigured to reverse the pump to reflux fluid from the aspirationconduit pathway and into the eye to help clear occlusions.

In another aspect, the invention provides an eye treatment systemcomprising an irrigation conduit pathway for directing an irrigationflow into the eye. An aspiration conduit pathway aspirates material fromwithin the eye. The aspiration conduit pathway is subject to a compliantreduction in volume induced by an occlusion of the aspiration flow. Apressure sensor is coupled to the aspiration conduit pathway fortransmitting a pressure therefrom. A controller is coupled to theaspiration conduit pathway. The controller is configured to effectintroduction of fluid into the aspiration conduit pathway in response tothe pressure, so that a maximum reflux pressure within the aspirationconduit pathway adjacent the eye is less than or substantially equal toa predetermined pressure, for example, the irrigation flow pressureadjacent the eye. Hence, reflux into the eye may be generated at leastin part by momentum in the aspiration conduit pathway toward the eye.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates an eye treatment system in which acassette couples an eye treatment probe with an eye treatment console,along with a method for use of the system for treating the eye of apatient.

FIG. 1A is a schematic side view of a method of treating an eye usingthe system of FIG. 1, showing the differing heights of variouscomponents of the treatment system and their effect on pressures of thesurgical fluids.

FIGS. 2A and 2B illustrate alternative cassettes having surgical fluidpathway networks for use in the system of FIG. 1.

FIG. 3 is a perspective view showing an exemplary embodiment of an eyetreatment cassette and the receptacle of the console for mounting thecassette, along with associated components of the console.

FIG. 3A is a perspective view similar to that of FIG. 3, in which thecassette is mounted to the receptacle of the console.

FIG. 3B is a front view showing the receptacle of the console andcomponents of the console that interface with the cassette.

FIG. 4 is a perspective view of an exemplary surgical fluid cassette foruse in the system and method of FIGS. 1 and 1A.

FIGS. 5A and 5B illustrate a back or interface surface of the cassetteof FIG. 4 showing the fluid pathway elements assembled within thecassette body (in FIG. 5A) and in an exploded format (in FIG. 5B).

FIG. 6 is a perspective view illustrating an exemplary pressure sensorassembly of the cassette.

FIG. 7A graphically illustrates pressures measured by the pressuresensor of the cassette over time, showing the effects of an occlusionand reflux used to clear that occlusion.

FIG. 7B graphically illustrates reverse peristaltic pump flows asdetermined from sensed pressure for use in the system of FIGS. 1 and 1A.

DETAILED DESCRIPTION OF THE INVENTION

The present invention generally provides improved devices, systems, andmethods for treating an eye of a patient. Exemplary embodiments provideimproved techniques for directing fluids into an aspiration conduitpathway between an eye and an eye treatment console for clearingocclusions and the like, particularly during treatments within aninterior of the eye.

In many embodiments, an eye treatment probe handpiece will be coupled toan eye treatment console by a cassette mounted to the console. Thecassette may include a surgical fluid network, typically including anirrigation conduit pathway for directing irrigation fluid toward the eyeand an aspiration conduit pathway for directing material (typicallyincluding both fluid and tissue) from the eye. The fluid network of thecassette may include resiliently deformable tubing, flexible (but lesscompressible or expandable) tubing, a pressure sensing mechanism, aholding tank or chamber, and/or the like. The cassette and console mayuse a volumetric pump to aspirate the material from within the eyethrough the aspiration conduit pathway. Other embodiments may employ avacuum source such as a vacuum pump (optionally being a Venturi pump ora rotary vane pump) or a connector for attachment to a vacuum system ofthe operating room. Exemplary embodiments may optionally include both avolumetric peristaltic pump and a vacuum source, with the operator orcomputer controller selecting between the aspiration drive mechanisms.Regardless, the cassette will often comprise a disposable structure thatseparates the surgical fluids from more expensive and reusablecomponents of the console. Other embodiments may include a reusablecassette body and disposable or sterilizable tubing.

Referring now to FIG. 1, a system 10 for treating an eye E of a patientP generally includes an eye treatment probe handpiece 12 coupled to aconsole 14 by a cassette 16. Handpiece 12 generally includes a handlefor manually manipulating and supporting a probe tip. The probe tip hasa distal end which is insertable into the eye, with one or more lumensin the probe tip allowing irrigation fluid to flow into the eye.Aspiration fluid may also be withdrawn through a lumen of the probe tip,with the console generally including a vacuum aspiration source, avolumetric aspiration pump, or both. Flexible conduits 18 of thecassette 16 help avoid direct contact between irrigation and aspirationfluids flowing to or from the eye and the components of the console 14.

When the distal end of the probe tip of handpiece 12 is inserted into aneye E (for example) for removal of a lens of a patient with cataracts,an electrical conductor (not shown) may supply energy from console 14 toan ultrasound transmitter of the handpiece. This ultrasound energy helpsto fragment the tissue of the lens, which can then be drawn into a portof the tip by aspiration flow. Alternatively, the handpiece may beconfigured as a vitrectomy probe or an irrigation/aspiration (I/A)probe. So as to balance the volume of material removed by the aspirationflow, an irrigation flow through handpiece 12 (or a separate probestructure) may be provided, with both the aspiration and irrigationflows being controlled by a controller 40 of console 14. In otherembodiments, the handpiece 12 may be configured to remove vitreousmaterial in the posterior chamber of the eye E, for example, byincluding an electrically or pneumatically driven cutter blade.

Controller 40 may include an embedded microcontroller and/or many of thecomponents of a personal computer, such as a data bus, a memory, inputand/or output devices (including a touchscreen user interface 42 and afoot pedal input device 44), and the like. Controller will often includeboth hardware and software, with the software typically comprisingmachine readable code or programming instructions for implementing one,some, or all of the methods described herein. The code may be embodiedby a tangible media such as a memory, a magnetic recording media, anoptical recording media, or the like. Controller 40 may have (or becoupled to) a recording media reader, or the code may be transmitted tocontroller 40 by a network connection such as an internet, an intranet,an Ethernet™, a wireless network, or the like. Along with programmingcode, controller 40 may include stored data or correlations forimplementing the methods described herein, and may generate and/or storedata that records parameters corresponding to the treatment of one ormore patients. Many components of console 14 may be found in or modifiedfrom known commercial phacoemulsification systems from Advanced MedicalOptics Inc. of Santa Ana, Calif.; Alcon Manufacturing, Ltd. of FortWorth, Tex.; Bausch and Lomb of Rochester, N.Y., and other suppliers.

Referring now to FIG. 1A, accurate surgical fluid flows into and/or outof eye E from system 10 will often benefit from information regardingpressures within the aspiration and/or irrigation conduit pathways. Ingeneral, a pressure sensor 64 may generate signals indicating pressurewithin the aspiration conduit pathway. The processor of console 14 maymake use of the pressure signals from sensor 64 to drive an aspirationpump, and the like.

While the pressure measured by sensor 64 is adequate for many purposes,the pressure within the aspiration conduit pathway defined by the probetip lumen and other structures of handpiece 12, by flexible tubing 18,and/or by the other fluid network elements of cassette 16 at locationsdifferent than that of pressure sensor 64 may also be of interest. Forexample, it may be beneficial to determine a pressure within theaspiration conduit pathway adjacent eye E. As eye E may generally be ata height HE that is different than the height of the sensor HS, thepressure within the aspiration conduit pathway adjacent eye E may bedetermined at least in part from the pressure head or heightdifferential between the height of the eye HE and the height of thesensor HS.

A wide variety of structures and techniques may be used to measure theheight of the eye HE, including providing appropriate sensors in (orcoupled to) handpiece 12, by determining a height of the operating tableor other patient support structure, or the like. As the height of theeye HE may differ for different patients and different system users,console 14 may include an input for receiving some information regardingthe height of the eye, such as by the system user inputting an estimatedheight of the eye, a sensor used to measure the height of a structurethat may be at least partially associated with a height of the eye, orthe like. In the exemplary embodiment, the processor of console 14 mayestimate a height of the eye HE from the height HT of an accessory tray22.

Accessory tray 22 may be supported by an articulatable linkage 24, withone or more joints of the linkage having a sensor coupled to theprocessor of console 14. Accessory tray 22 generally holds tools and/ormedication used during treatment of eye E, and is flexibly moved byarticulating linkage 24 so that tray 22 is near the eye. There may besome slight offset in height between the height of the tray HT and theheight of the eye HE, the tray optionally being at or slightly below theeye for convenient access to the contents of the tray without blockingaccess to eye E during the use of handpiece 12. Typically, the height ofthe tray HT is between about 0 and 8 inches below the height of thesensor HS, depending on the structure of tray 22, the use and structureof handpiece 12, physician preferences, and the like. A standard offsetmay be applied by processor 40 of console 14 (see FIG. 1), individualoffsets may be applied for particular surgeons or system users, and/orthe system user may input a measured or estimated difference in heightbetween tray 22 and eye E for each procedure on a particular patient oreye. In some embodiments, aspiration and/or irrigation pressure headsmay be determined by processor 40 based on an assumption that the eyeheight HE is at or above the tray height HT. For example, to beconservative the eye may simply be assumed to be at the lowest traylevel within the range of movement of the tray, such as 8 inches belowthe height of the sensor HS. Regardless, the processor of console 14 maymake use of the sensed height HT of tray 22 to determine a head pressuredifferential between the measured pressure 64 and the pressure withinaspiration conduit pathway adjacent eye E.

Still referring to FIG. 1A, differential head pressures may also be usedby the processor of console 14 to determine an irrigation pressurewithin an irrigation conduit pathway adjacent eye E. An irrigationcontainer 26 is supported at an irrigation fluid height HF, with theheight of the irrigation fluid varying with a height of a fluid support28. The fluid support 28 may have a sensor to indicate the height of thefluid HF to the system processor of console 14, and/or fluid support 28may be driven by an actuator to vary the height of the fluid and hencethe irrigation fluid pressure within the irrigation conduit pathwayadjacent eye E. The processor 40 may determine the irrigation fluidpressure adjacent eye E from the difference in height between the fluidheight HF and the height of the eye HE based on the height of the trayHT and any offsets between the tray and eye.

Referring now to FIG. 2A, elements included in the aspiration andirrigation fluid flow network of an eye treatment system employing afirst exemplary cassette 16 a are shown. As described above, irrigationsource 46 typically provides irrigation fluid pressure by relying atleast in part on a gravity pressure head that varies with a height of anirrigation container 26 (see FIG. 1A) or the like. An irrigation on/offpinch valve 48 may include a short segment of a resilient flexibleconduit of cassette 16 b, which can be engaged and actuated by anactuator of the console. A surface of a cassette body 78 may be disposedopposite the actuator to facilitate closure of the conduit lumen.Alternative irrigation flow systems might include volumetric pumps,alternative fluid pressurization drive systems, fluid pressure or flowmodulating valves, and/or the like. Regardless, the irrigation networkgenerally defines an irrigation fluid conduit path 47 between irrigationsource 46 and an irrigation port on the insertable probe tip ofhandpiece 12.

In cassette 16 a, an aspiration flow network 50 generally provides anaspiration flow path that can couple an aspiration port in the probe tipof handpiece 12 to either a peristaltic pump 54 and/or a holding tank56. Fluid aspirated through the handpiece may be contained in holdingtank 56 regardless of whether the aspiration flow is induced byperistaltic pump 54 or the vacuum applied to the holding tank. Whenvalve 58 is closed and peristaltic pump 54 is in operation, pumping ofthe aspiration flow may generally be effected directly by theperistaltic pump, independent of the pressure in the holding tank 56.Conversely, when peristaltic pump 54 is off, flow through theperistaltic pump may be halted by pinching of the elastomeric tubing ofthe peristaltic pump by the rotors of the peristaltic pump drive of theconsole. Regardless, the pressure within tank 56 may be maintained at acontrolled vacuum level, often at a fixed vacuum level, by a vacuum pumpsystem 44 of the console. Aspiration flow that drains into tank 56 maybe intermittently removed by peristaltic drain pump 60 and directed to adisposal fluid collection bag 62.

The operation of aspiration flow network 50 may be understood by firstconsidering the aspiration conduit pathway 51 when valve 58 is closed.In this mode, peristaltic pump 54 draws fluid directly from handpiece12, with a volumetric peristaltic pump flow rate being controlled by thesystem controller. To determine the appropriate flow rate, the level ofvacuum within the aspiration flow network may be identified using vacuumsensor 64 disposed along the effective aspiration conduit pathwaybetween peristaltic pump 54 and the aspiration port of handpiece 12.While the aspiration material flows through holding tank 56 andeventually into control bag 62, the holding tank pressure may havelittle or no effect on the flow from the handpiece in this mode.

When peristaltic pump 54 is not in operation, rotation of theperistaltic pump is inhibited and the rotors of the peristaltic pumppinch the arcuate resilient tubing of the pump so as to block aspirationflow. Material may then be drawn into the aspiration port of handpiece12 by opening selector valve 58. When valve 58 is open, the aspirationport draws fluid therein based on the pressure differential betweenholding tank 56 and the chamber of the eye in which the fluid port isdisposed, with the pressure differential being reduced by the totalpressure loss of the aspiration flow along the aspiration path betweenthe tank and port. Regardless, cassette 16 a allows the eye treatmentsystem to operate in either peristaltic or vacuum-based pumping modes.

Referring now to FIG. 2B, in some embodiments a system user will performtreatments which may only employ peristaltic pumping. Hence, alternativecassette 16 b includes a somewhat simpler aspiration flow network havinga single aspiration conduit pathway 53 coupling an aspiration port ofhandpiece 12 to peristaltic pump 54. Hence, alternative cassette 16 bmay operate in a manner similar to that described above regarding theuse of cassette 16 a when selector valve 58 is closed, with theexception that the aspiration fluid downstream of the peristaltic pump54 is transmitted directly to collection bag 62 (rather than via holdingtank 56). In some embodiments of these structures and methods, a vacuumsource alone may be used to drive aspiration flow.

Regardless of whether the volumetric and/or vacuum pump capabilities ofcassette 16 a are available, or whether only volumetric pumping isavailable through alternative cassette 16 b, the aspiration port orports of handpiece 12, and/or the aspiration conduit network downstreamof the port(s) may occasionally become occluded during use. When usingvolumetric pumping, occlusion of the aspiration conduit pathway whileperistaltic pump 54 is turning results in a reduction in pressure alongthe aspiration conduit pathway between the occlusion and pump, which canoften be detected at vacuum sensor 64. Some of the tubing along thepathway may be resilient tubing to facilitate closure of pinch valvesand the like. Other portions of the aspiration conduit pathway may bedefined by flexible tubing which is somewhat stiffer in cross-section soas to limit the change in volume of the aspiration conduit pathwayinduced by an occlusion. Nonetheless, the pressure reduction caused bythe occlusion will typically cause some, and often a significant, changein the total volume of the aspiration conduit pathway.

In many cases, application of ultrasound energy by the probe tip willrelatively quickly clear an occlusion with little or no action taken bythe surgeon or other system operator. The controller of the console mayvary the peristaltic pumping speed in response to a change in sensedvacuum level in such cases, where the occlusion may clear quickly enoughthat no operating changes are required. However, other occlusions maycontinue to block the aspiration flow even after the peristaltic pump 54is completely halted, and/or after the system user inputs a command tohalt aspiration flow.

As schematically illustrated in FIG. 1, operation of system 10 andhandpiece 12 may, at least in part, be controlled using foot pedal 44.For example, no surgical fluid flows or energy may be delivered to theprobe when foot pedal 44 is in a nominal or zero position. When thesystem operator presses foot pedal 44 to a first position 1, irrigationflow may be commenced by opening of the irrigation pinch valve.Aspiration flow may be added to the irrigation flow by positioning thefoot pedal 44 at a second position 2, with the application of ultrasoundenergy to the probe tip being added at foot position 3. When the systemuser determines that flow through the aspiration conduit pathway hasbeen occluded and does not appear to be opening in a reasonable amountof time despite the application of ultrasound energy, foot pedal 44 maybe returned to its nominal position zero to temporarily halt thetreatment of eye E while the occlusion is cleared.

Referring again to FIGS. 2A and 2B, various venting and refluxapproaches may be used in connection with the systems described hereinto help clear occlusions and the like. At least two different approachesmay be applied to clear occlusions: venting of the aspiration system andreflux. Venting generally refers to introduction of fluids into theaspiration conduit pathway so as to decrease a level of vacuum withinthe conduit pathway (e.g., increase the absolute pressure within theaspiration conduit pathway) without refluxing material into the eye.Such a reduction of the vacuum may help allow oversize tissue fragmentsto be cleared from an outer surface of the probe tip. Reflux refers tocausing fluid from within the aspiration conduit pathway to flow throughthe aspiration port(s) and into the eye (or other environmentsurrounding the aspiration port when the aspiration occurs), optionallyby introduction of fluid into the pathway. Reflux may help clearobstructions from over the outer surface of the probe tip, obstructionswedged or otherwise disposed at least partially within the aspirationport, and/or obstructions or occlusive material which has entered intothe aspiration conduit pathway by expelling the occlusions from theprobe. While they can be related and in some embodiments may becombined, venting may be employed without inducing reflux.

Various venting and reflux methodologies may be used during ophthalmicsurgical procedures, particularly those procedures which make use ofpumps for aspiration of material from the eye (including volumetricpumps such as a peristaltic pump, vacuum pumps such as a Venturi pump orrotary vane pump, and the like). Preferred methodologies will often haveboth a relatively fast response time and allow accurate control over thepressures and/or flows within the aspiration conduit pathway.

Referring once again to FIG. 2B, venting and/or aspiration mayoptionally be provided using an irrigation vent valve 55. The aspirationconduit pathway may be vented using such a vent valve, with the ventvalve optionally providing fluid communication between the aspirationconduit pathway and a source of fluid at a higher pressure than that ofthe aspiration line, such as the irrigation conduit pathway 47. Inalternative embodiments, venting may be provided to the atmosphere orthe like, although venting to the irrigation line may provide a fasterresponse due to the enhanced pressure of the irrigation flow. Venting tothe higher pressure irrigation fluid may enhance response time, thoughmay also benefit from additional care to provide adequate pressurecontrol within the aspiration conduit pathway during venting. Inexemplary venting systems relying on a vent valve to irrigation flow,atmospheric pressure, and/or the like, irrigation vent valve 55 willpreferably allow both on/off control of the venting flow into theaspiration conduit pathway, together with venting modulation control tovary the venting flow in response to signals from vacuum sensor 64.While use of a vent valve that allows modulation provides a relativelysimple mechanical structure for cassette 16 b, accurate modulation ofvent flow into the aspiration conduit pathway to provide both goodresponse time and accurate control may involve calibration of the ventvalve properties, replacement of a simple standard pinch valvearrangement with a modified structure (for example, having an elongateactuator surface engaging a significant length of flexible vent conduittubing along the direction of venting flow to provide repeatable andreliable throttling), and/or the like.

Alternative venting and/or reflux methodologies may employ the structureof peristaltic pump 54 to introduce fluid into the aspiration conduitpathway and/or to induce reflux from the port of the handpiece probetip. Venting and/or reflux may be provided by reversing the direction ofrotation of the peristaltic pump from its normal operation. Thisreversal of the peristaltic pump may cause fluid to be controllablyintroduced into the aspiration conduit pathway and toward handpiece 12.By controlling both the direction and rate of rotation of the pump, thepressure in the aspiration line may be precisely controlled, often witha feedback from vacuum sensor 64. In addition, the pump and associatedelectronic controller of the console can be configured to provide anadvantageously fast response time. In some embodiments, by using theexisting peristaltic pump for venting and/or reflux, a valve that mightotherwise be included for venting of the aspiration line may either beused for other purposes or eliminated altogether, as can be understoodwith reference to FIGS. 2A and 2B. Hence, the cassette body 78 ofcassette 16 a (shown in FIG. 2A) may be configured by mounting ofappropriate fluid network elements thereon for use with vacuum and/orperistaltic pumps, or as shown in FIG. 2B as alternative cassette 16 bwhen relying only on a peristaltic pump for aspiration. Console 14 maymake use of the same two pinch valve actuation structures for use eitheras a selector valve 58 or an irrigation vent valve 55, depending on theconfiguration of the cassette. In some embodiments, a combinationventing system may be employed in which reversal of the peristaltic pumpis combined with opening and/or modulation of an irrigation vent valve55.

When relying on peristaltic pump 54 to provide venting and/or reflux incassette 16 a or alternative cassette 16 b, venting and/or reflux maygenerally be provided by rotating the pump head in an opposite direction(e.g., counterclockwise in FIG. 2A). As will be described below withreference to FIGS. 7A and 7B, exemplary embodiments may effect refluxfrom the probe tip without pumping sufficient fluid into the aspirationvent line so that the aspiration conduit pathway adjacent the port has ahigher static pressure than an irrigation pressure and/or fluid pressuregenerally within eye E. As it may be advantageous to avoid inducingexcessive reflux into the eye and overpressurizing the eye, reflux maybe induced by the momentum of fluid vented into the aspiration conduitpathway, and by halting flow into the aspiration conduit pathway whenthe signals from vacuum sensor 64 indicate that the pressure of theaspiration fluid adjacent the eye (when the differential head pressureis accounted for between the height of the eye and the height of thepressure sensor) is substantially equal to or less than the irrigationpressure at the eye (and hence the pressure within the eye itself).While the pressure of the aspiration conduit pathway adjacent the eyethat is induced may be less than, equal to, or very slightly greaterthan the pressure within the eye, the pressure will remain substantiallyequal to or less than the pressure within the eye so long as reflux flowis induced largely by the momentum of fluid within the aspirationconduit pathway (rather than being induced by a positive pressuredifferential). In certain embodiments, reflux may be primarily inducedby the momentum, with some embodiments being induced solely by themomentum.

While the reflux described herein will often be generated by reversal ofperistaltic pump 54 and/or modulation of irrigation vent valve 55, stillfurther alternative venting and/or reflux methodologies may be used toinduce the momentum-induced reflux described herein. For example, theentire pump head of peristaltic pump 54 could be translated, with thepump head shown in FIGS. 2A and 2B being moved to the left in order tomove fluid back toward the handpiece.

Exemplary cassette, receptacle, and fluid network structures areillustrated in FIGS. 3-6. Referring first to FIG. 3, in the exemplaryembodiment cassette 16 can be advanced along a mounting axis 76 whilethe cassette is manually supported until the surfaces of the cassettebody engage receptacle surfaces of console 14. C-shaped channels defineat least a portion of the receptacle, and can be driven to automaticallydraw the cassette 16 into a fully mounted position on console 14 alongmounting axis 76. Automated mounting may be actuated by a microswitch90, and helps provide the desirable engagement forces between theperistaltic pump rotor 54 b, a peristaltic pump rotor 54 b, aperistaltic pump drain rotor 60 b, and other components of the consolewith the corresponding fluid network elements of cassette 16. A pressuredetection surface 64 b is also seen in FIG. 3, with the detectingsurface engaging a surface of the pressure sensor of the console so asto transmit a signal to the processor of console 14 indicating thepressure along the aspiration conduit pathway.

FIG. 3A is an illustration similar to that of FIG. 3, with cassette 16here being fully mounted in receptacle 92 of console 14. The consoleincludes a support structure 94 that generally supports receptacle 92,and a molded polymer cassette body 78 that generally provides supportfor the fluid network elements included within the cassette.

An exemplary arrangement of the console components exposed to receptacle92 for interaction with the network elements of the cassette is shown inFIG. 3B. As mentioned above, peristaltic drive rotors 54 b and 60 bdrive aspiration and drain pumps, respectively. An irrigation pinchvalve actuator 48 b moves to open or close irrigation flow through theirrigation conduit network, while a selector valve actuator 58 b may beused for selecting between peristaltic pumping or vacuum pumping whencassette 16 a is mounted thereon, or may be used as an irrigation ventvalve 55 b when cassette 16 b is mounted thereon. (See FIGS. 2A and 2B)Hence, in some embodiments, actuator 58 b may provide both on/offactuation and modulation of the associated flows.

A vacuum coupler 72 b, preferably in the form of an axiallyspring-loaded nipple, provides coupling between the vacuum pump system44 of console 14 and a vacuum coupler of holding tank 56 of thecassette. A waste fluid detector 74 b may be used to identify whenenergizing of a drain pump 60 is appropriate.

Referring now to FIGS. 4, 5A, and 5B, the structure of an exemplarycassette 16 a may be better understood. Cassette 16 a generally includesmolded polymer cassette body 78 with the cassette body defining thepositioning surfaces that engage the receptacle of the console. Flexibletubing 18 couples the cassette to an irrigation fluid supply, couplesthe aspiration and irrigation flow networks to the handpiece, anddefines elements of the fluid networks such as pinch valves andperistaltic arc segments 54 a and 60 a for the aspiration pump and drainpump, respectively. The vacuum coupler 72 a provides communication withholding tank 56 and interfaces with the vacuum connector of the console,while a vacuum sensor assembly 64 a has a surface that deflects withchanging pressure along the aspiration conduit pathway. A simple polymerfluid disposal bag 132 may be mounted to cassette body 78, with thedisposal bag receiving outflow from the drain pump. The location offlexible tubing segments used for the irrigation fluid pinch valve 48 aand for the selector valve 58 a are seen in FIG. 5B.

Sensor assembly 64 a is shown in more detail in FIG. 6. A housing 162 issealed by a displaceable surface 164, with the displaceable surfacemoving along an axis 166 in response to changes in pressure within thehousing. A lid 168 disposed over the displaceable surface allowsmovement of the surface along the axis.

Referring now to FIG. 7A, exemplary variations in pressure that may bemeasured by a pressure sensor during occlusion and venting or reflux canbe understood. The pressure measured by the pressure sensor begins tochange with the initiation of aspiration flow 180, with the pressureeventually reaching a substantially steady state during normal operation182. Slight variations in pressure during this time may be encountereddue to pulsation effects of the peristaltic pump, minor occlusions(which are cleared without the system or user taking action), or thelike. However, a significant pressure excursion begins when the probetip is inflicted with a hard occlusion 184 which is not quickly clearedor resolved by the ultrasound energy through the tip or the like.

The pressure excursion experienced as a result of hard occlusion 184includes a significant decrease in the pressure measured by the sensoralong the aspiration conduit pathway. To resolve the hard occlusion, thesystem user may input a command to the system by releasing the footpedal, so that the foot pedal returns to its nominal or zero position(alternatively, the system may automatically initiate action based onthe sensed aspiration pressure or some other system parameter). Assumingthe hard occlusion is sufficient to effectively seal the aspirationport, the vent or selector valve remains closed, and the peristalticpump is not turning (with the rotors thereby pinching the aspirationconduit pathway in a sealed configuration), the measured pressure mightthen remain steady (or the amount of vacuum gradually diminish and thenegative pressure below atmospheric gradually increase) unless someaction is taken to help remove the occluding material. Toward that end,in response to input from the system user, the peristaltic pump may bedriven in a reverse direction so as to introduce fluid back into theaspiration conduit pathway between the aspiration pump and theaspiration port. Note that any driving of the aspiration pump with thefoot pedal in the nominal or off position represent a departure fromdrive protocols of some or all standard commercial phacoemulsificationsystems. As described above regarding FIG. 2B, alternative systems mayemploy opening and/or modulation of a vent valve in response to theinput command from the system user, and the input command may take avariety of different forms including actuation of a command to clear theocclusion via a keyboard, a button on the handpiece, a touchscreeninterface, or the like. Regardless, fluid can be introduced into theaspiration conduit pathway between the pump and aspiration port in acontrolled manner in response to the command.

Still referring to FIG. 7A, the introduction of fluid may result in apressure 188 measured at the pressure sensor that is different than(often being slightly higher, though it may be lower in someembodiments) than a pre-aspiration pressure 190. The pressuredifferential 192 may compensate for differences between the height ofthe sensor HS and height of the eye HE, optionally as determined fromthe height of the tray HT as explained above regarding FIG. 1A.Nonetheless, the steady state final pressure 188 used to clear theocclusion may still result in a pressure within the aspiration conduitpathway adjacent the eye which is substantially equal to or less thanthe pressure of fluid within the eye or irrigation pressure adjacent theeye. Some slight pressure overshoot may occur before the steady statefinal pressure 188 is obtained at the sensor, although suitable reversepumping drive characteristics and/or vent valve modulationcharacteristics can limit such overshoot to safe levels. In someembodiments, the system may approach the steady state pressure with thecharacteristics of a critically damped system, with the sensed pressureovershooting the steady state pressure a single time and then graduallyapproaching the steady state pressure (e.g., as illustrated by thedashed curve in FIG. 7A).

Referring now to FIG. 7B, an exemplary reverse peristaltic pump drivescheme for venting or reflux is graphically illustrated. When a commandto clear an occlusion is entered by the system user, or in someembodiments, when the system processor determines the clearing of anocclusion is appropriate (such as when a reflux switch is engaged or thefoot pedal returns to the nominal or off position and the pressuresignal remains at a significant vacuum or negative pressure), the systemprocessor may energize the peristaltic pump to turn in a reversedirection at a commanded speed, thereby resulting in a reverse ornegative aspiration pump flow (indicated by negative cubic centimetersper minute or ccm). So long as the sensed vacuum at the sensor remainsat or below negative 50 mmHg, the system controller may, for example,command the peristaltic aspiration pump to generate a negative 60 ccmaspiration flow 194. More generally, an initial reverse pumping rate maybe maintained whenever sensed pressures are below a pressure in a rangefrom about 0 mmHg to negative 650 mmHg, optionally from about negative50 mmHg to about negative 100 mmHg, typically being from about negative40 mmHg to about negative 80 mmHg.

Once the aspiration flow begins to moderate the level of vacuum measuredby the sensor, it will often be advantageous to decrease the reversepumping flow. For example, once the sensed negative pressure is above athreshold level of negative 50 mmHg, the processor may determine anappropriate reverse pumping flow rate (or alternatively pump speed) froma linear correlation 196 between the sensed vacuum and the flow rate (oralternatively pump speed). An exemplary correlation provides a linearrelationship throughout the range of 50 mmHg of negative pressure to 0.0mmHg or atmospheric pressure.

To avoid excessive overshoot in the pressure or overpressurization ofthe eye, the overall correlation between reverse pumping flow rate andsensed negative pressure may include a second correlation portion 198having a different (and often smaller) slope once the pressure withinthe aspiration conduit pathway adjacent the eye approaches the internalpressure of the eye and/or irrigation fluid pressure at the eye. In theexemplary system, the system processor linearly decreases the reversepumping flow rate from negative 25 ccm to negative 15 ccm as the sensedpressure varies between atmospheric and the stopping point. The slope ofthe linear correlation 196 may vary. For example, the flow rate when thesensed pressure reaches atmospheric pressure may be anywhere from aboutzero ccm to a flow rate that is at or about equal to the flow rate whenthe pump begins to slow down (negative 60 ccm in the presentembodiment). In some embodiments, the second linear correlation 198 isinitiated either before or after the sensed pressure is equal toatmospheric.

Reverse pumping of the aspiration flow pump may be halted once thesignals from the aspiration vacuum sensor indicate that the pressurewithin the aspiration conduit pathway adjacent the eye is equal to ornear the irrigation fluid pressure adjacent the eye. The calculations todetermine the halting point can be understood with the description aboveof FIG. 1A. If the halting pressure has not been reached within someappropriate predetermined time range of initiation of reverse pumping,such as within about 3 seconds of initiation of reverse pumping, reversepumping may be halted before the target pressure has been reached. Notethat the target termination pressure 200 in the illustrated embodimentmay vary depending on the height of the eye (optionally as determinedfrom the height of the tray), the height of the fluid supply for theirrigation fluid, and the like. Hence, the slope of the correlation 198may also vary for different patients, surgeon preferences, or proceduretypes. Regardless, the flow rate will generally go to zero once thesensed pressure is equal to or greater than a predetermined end pointpressure, or when the time limit for reverse pumping has been reached.

The exemplary overall correlation between sensed pressure and reversepumping flow rate illustrated in FIG. 7B generally includes threepressure ranges or correlation portions 194, 196, and 198, with theslope of the correlation differing between these different ranges.Alternative embodiments may employ more than three ranges or less thanthree ranges, and/or may employ non-linear relationships between thepressures and flow.

While the exemplary embodiments have been described in some detail forclarity of understanding and by way of example, a variety ofmodifications, changes, and adaptations will be clear to those of skillin the art. Hence, the scope of the present invention is limited solelyby the appended claims.

1-12. (canceled)
 13. An eye treatment method comprising: directing anirrigation flow into the eye through an irrigation conduit pathway;aspirating material from within the eye by drawing an aspiration flowthrough an aspiration conduit pathway; in response to an occlusion ofthe aspiration flow, the occlusion inducing a compliant reduction involume of the aspiration conduit pathway, introducing fluid into theaspiration conduit pathway; and controlling the introduction of fluidinto the aspiration conduit pathway in response to a pressure along theaspiration conduit pathway by changing the pump speed to provide areduced reverse flow rate when the pressure in the aspiration conduitpathway is at atmospheric pressure and so that a maximum reflux pressurewithin the aspiration conduit pathway adjacent the eye is less than orsubstantially equal to an irrigation flow pressure adjacent the eye, andso that reflux into the eye is largely generated by momentum in theaspiration conduit pathway toward the eye.
 14. An eye treatment systemcomprising: an eye treatment probe; an eye treatment console having acontroller and an aspiration pump drive; and a cassette coupling theprobe to the controller, the cassette having an irrigation conduitpathway for directing an irrigation flow into the eye via the probe, thecassette and probe having an aspiration conduit pathway coupled to thepump for aspirating material from within the eye; a pressure sensor forproviding a sensed pressure indicating pressure within the aspirationconduit pathway; a first function correlating the sensed pressure and areverse pump speed, or correlating the sensed pressure and a reverseflow rate; a second function correlating the sensed pressure and thereverse pump speed, or correlating the sensed pressure and the reverseflow rate; the controller configured to select between the firstfunction and the second function when the sensed pressure is within apredetermined pressure range, the controller further configured tocontrol the reverse pumping flow rate based on the selected function.15. The system of claim 14, wherein during an occlusion of theaspiration flow, reverse the pump to reflux fluid from the aspirationconduit pathway and into the eye to help clear the occlusion, and tochange the pump speed to provide a reduced reverse flow rate when thepressure in the aspiration conduit pathway is at atmospheric pressure,wherein the pump comprises a volumetric pump, wherein the occlusioninduces a compliant reduction in volume of the aspiration conduitbetween the eye and the pump, and wherein the controller is configuredso that the reversing of the pump at least partially compensates for thereduction in volume.
 16. The system of claim 14, wherein the controlleris configured so that reversing of the pump is halted when a pressure ofthe aspiration flow adjacent the eye is less than or substantially equalto an irrigation flow pressure at the eye so that the reflux into theeye is largely generated by momentum in the aspiration conduit pathwaytoward the eye.
 17. The system of claim 14, wherein the controller isconfigured to maintain a substantially constant initial reverse pumpingflow rate while the pressure along the aspiration conduit pathwaycomprises a vacuum greater than a vacuum threshold.
 18. The system ofclaim 14, wherein the controller is configured to determine a reducedreverse flow rate or a reduced reverse pump speed from the sensedpressure, when the sensed pressure is between a vacuum threshold andatmospheric pressure, so that the reduced reverse pumping flow decreaseslinearly with decreasing vacuum.
 19. The system of claim 18, wherein thecontroller is configured to determine the reduced reverse flow rate orthe reduced reverse pump speed from the pressure, when the sensedpressure is more than atmospheric pressure and when a pressure of theaspiration flow adjacent the eye is less than an irrigation flowpressure at the eye, so that the reduced reverse pumping flow decreaseslinearly with increasing pressure.
 20. The system of claim 14, furthercomprising a foot pedal input having a nominal undeflected position, afirst position associated with irrigation flow, and a second positionassociated with irrigation flow and aspiration flow, and wherein thecontroller is configured to reverse the pump when the foot pedal inputdevice is released back to the nominal position in response to anocclusion along the aspiration conduit pathway.
 21. The system of claim14, wherein first function and the second function are each linearfunctions, the second function having a slope that is different from thefirst function.
 22. An eye treatment method comprising: directing anirrigation flow into the eye through an irrigation conduit pathway;aspirating material from within the eye by drawing an aspiration flowthrough an aspiration conduit pathway with a pump; and in response to anocclusion of the aspiration flow, reversing the pump and refluxing fluidfrom the aspiration conduit pathway and into the eye to help clear theocclusion.